Remove unused import
Remove unused import

wkentaro/chainer,chainer/chainer,keisuke-umezawa/chainer,ktnyt/chainer,hvy/chainer,wkentaro/chainer,okuta/chainer,hvy/chainer,chainer/chainer,chainer/chainer,keisuke-umezawa/chainer,niboshi/chainer,jnishi/chainer,hvy/chainer,okuta/chainer,ktnyt/chainer,keisuke-umezawa/chainer,jnishi/chainer,niboshi/chainer,wkentaro/chainer,ktnyt/chainer,niboshi/chainer,okuta/chainer,keisuke-umezawa/chainer,hvy/chainer,rezoo/chainer,niboshi/chainer,wkentaro/chainer,jnishi/chainer,ktnyt/chainer,jnishi/chainer,pfnet/chainer,tkerola/chainer,chainer/chainer,okuta/chainer